Process of grinding gears



March 5, 1935. s gw (1,993.120

v PROCESSv OF GRINDING GEARS Filed Jun'eko, 1934 2 Sheets-Sheet i attorney j i March 1935. A. L. STEWART PROCESS OF GRINDING GEARS Filed June 20, 1934, 2 Shets-Sheet z Patented Man 5,1935 '1,993,1zo'

UNITED STATES PATENT OFFICE.

PROCESS OF GRINDING GEARS Arthur L. Stewart, Rochester, N. Y., assignor to Gleason Works, Rochester, N. Y., a corporation of New York Application June 20, 1934, Serial No. 731,472

12 Claims. (CL 51-278) The present invention relates to the grinding eliminating the disadvantages of each.- It is of gears in a generating process and particularly therefore the purpose of the present invention to to the grinding of straight tooth bevel and hypo d p v -g inding method which will be gears. rapid and at the same time result in smooth tooth There are two principal methods employed in surfaces.

grinding gears by the generating process and In all grinding, whether with a conical or a these methods distinguish from one another basplane-sided wheel, it is customary to take one or ically in the types of grinding wheels employed. more roughing grinds around the gear, remov- In one method, the wheel used has a conical ing stock, and then to set in and take a final 'flni0 grinding surface which is inclined to the pitch ishing grind to secureasmooth tooth-surface fln- 10 surface of the gear in accordance with the presish. In the pres invention, I p p 0 use sure angle of the tooth surfaces to be ground and he coni al ide f a Wh el f r r u h rih i the tooth surfaces are generated by rotating the t e plane S de 01' a whee for t e fi h di wheel on its axis and reciprocating it across the In the preferred embodiment of the invention, I

1;: face of the gear while simultaneously producing a use a double-sided wheel, one side being conical relative rolling movement between the wheel and and the other side plan d k he ou h gear as though the gear to be ground were rolling grinds with the conical side of the wheel and then with a gear represented by the wheel. In the set over andtaketheflnish-grinds with the plane other method, the wheel used has a plane grinding side of the wheel.

20 surface and the wheel is so positioned relative to Pr f rably, w dou le-Sided Wheels are em- 20 the gear to be ground that the plane surface of pl y F 1 the r ri the tw Wheels the wheel is inclined to the pitch surface of the will preferably be positioned to operate on oppogear in accordance with the pressure angle of the site sides of the same tooth simultaneously. tooth surfaces. The grinding operation is eflfect- Their conical surfaces are'inclined to the Pitch ed by rotating the wheel on its axis while producu e 0 the 8 in accordance with h p ing the necessary rolling movement. The wheel ure angles 01 the toothsul'faees to be und nd mayor may not be reciprocated across the face of the gr d is effected by reciprocating, e the gear, as desired. The wheel may be made of wheels across the face of the gear while producing sufficiently large diameter to cover and grind the the required rolling generating motion. The diwhole length of the tooth surfaces of the gear in rections of the reciprocating motions will depend so which case no reciprocating motion is necessary. on the lengthwise directions of the tooth surfaces. Each of the above described methods has its ad- For finish-grinding, the wheels are repositioned vantages, and each its drawbacks. The conical with the plane surfaces of the wheels inclined to surfaced wheel has theoretically only point conthe -pitch surface of the gear inaccordance with tact at any instant with the tooth surfaces to be the pressure angles on the opposite sides of the ground and therefore the feed of such a wheel teeth and preferably so positioned that the plane can be quite coarse so that stock can be removed surfaces operate on opposite sides of alternate f m e Sides f the teeth of a gear quite pi y teeth of the gear. For tapered gears, the angles with Such a wheel without fear of burning the of convergence of the paths of the wheels must 40 tooth surfaces. When this type of wheel is used, also be readjusted between t rough and finish 0 however, the quality of finish of the tooth surgrinding operations, fo the angle f convergence faces depends primarily upon the number of or the tool paths, when the wheels are i y 1 strokes of the grinding wheel across the face of on opposite sides of the same teeth is much less the gear while each tooth surface is being rolled than the angle of convergence of the tool paths 4o out, and, even with extremely high stroke-speeds, hen the wheels are 0 rating on o posite sides it is not always possible to avoid so-called gener- 2 difierent teeth i flmsh indmgthe ating flats 913 the Sides. cube teeth being ground :vheels may be reciprocated if desired, but if their The fiat-sided wheel grinds a much smoother diameter islarge enough the reciprocating mow tooth surface and one without generating flats.

The flat-sided wheel has, however, a line contact ment can be P during the finish grinding 0 with the gear teeth and relatively fine feeds must t be used in gr nding with such a wheel if burn- The v nta e of the presen process are ing of the t 0th surfaces is to be avoided. manifold. 'First, the use of the conical side of the h-grinding permits of removing The purpose of the present invention is to com Wheel d t 8 E v bine the advantages of the two process s while stock very rapidlywithout danger of burning? that previously employed in grinding with a conical wheel because the smoothness of finish is nov longer dependent on the number of strokes of the wheel across the face of the gear during the rolling out of the tooth profiles. Third, as against any previous process of grinding gears with two wheels, the present method is most economical in the matter of wheels, since it makes use of both sides of a wheel. Fourth, this process reduces the possibility of errors in tooth spacing, since the first and last teeth which are rough-ground are-not, due to the set-over of the wheels, the same teeth as are first and last finish-ground. Finally, one of the added advantages of the present invention is that, with but few, if any, alterations, existing machines can be employed in grinding gears according to this invention. Thus, the

- invention has been illustrated in connection with the grinding of straight bevel gears on a grinder of the type covered by the pending application of 'Eyvind Finsen, Serial No. 603,541, filed April 6, 1932. Provision for sufiicient angular adjustment of the grinding wheel spindles to take care of the changes in positions of the wheels required in order to grind the correct pressure angles with either the conical sides or the plane sides of the wheels is all that is required to make this particular machine suitable for use in grinding gears according to the present invention. 7

The principal objects of the present invention have now been mentioned. Other objects of the invention will appear hereinafter from the specification and from the recital of the. appended claims.

In the "drawings:

Fig. 1 is a fragmentary end view showing the positions of the grinding wheels and gears in a rough-grinding operation according to the present invention; 1

Fig. 2 is a corresponding view showing the relative positions of the wheels and gear during finish grinding;

' Fig. 3 is a view at right angles to Fig. 1 and further illustrating the positions of the grinding wheels and gear during the rough-grinding operation, the gear ground being a straight bevel gear, some of whose teeth are shown in section and whose outline is indicated in dotted lines; and

Fig. 4 is a view taken at right angles to Fig. 2

and further illustrating, by contrast with Fig. 3, the positions of the grinding wheels in the finish grinding operation.

In the above views, the machine parts shown are parts of a machine such as has been described in the Finsen et al. application above mentioned.

In the drawings, G designates a bevelgear whose tooth surfaces are to be ground and 5 and 6 denote, respectively, a pair of grinding wheels which are to be employed in the grinding of the tooth surfaces of this gear. The wheels are provided on one side ,with truncated conical grindingsurfaces 7 and 8, respectively, and on their other sides with plane grinding surfaces 9 and 10, respectively, and the wheels are suitably secured as by means of nuts 11, to spindles 12. The spindles are journaled on anti-friction bearings 13 in heads 14 that .are adjustably mounted on tool-slides 15. The tool-slides are mounted, as shown, to reciprocate in tool-arms 16 and 17, re-

spectively. These arms are angularly adjustable, to determine the angle of convergence of the paths of travel of the wheels. The arms adjust angularly'about an axis 2:, and their angular adjustment can be effected by rotation of the screw shaft 18 which threads into the two heads 19 and 20-that are swivelly connected to studs which thread into the arms 16 and 17. The slides are reciprocated by rotation of the crank 22 which 'is' connected by the crank-arm 23, link 24, actuating member 25, bolts 26 and nuts 27 with the slides 15.

The grinding wheel spindles have pulleys 29 secured to them and are driven through these pulleys and belts 30 from motors mounted on the arms 16 and 17 or from any suitable source of power.

In the practice of my invention, the gear is, of course, first rough-ground. For this purpose, the grinding wheels 5 and 6 are adjusted relative to the gear G so that their conical surfaces 7 and 8, respectively, engage opposite sides 37 and 38, respectively, of a tooth 40 of the gear and so that these conical operating surfaces 7 and 8 are inclinedto the pitch surface of the gear at the angle required to produce correct pressure angle on the sides 37 and 38, respectively, of the teeth of the gear. This is shown in Fig. 1.

The arms 16 and 17 are also adjusted by the screw 18 in order to adjust the longitudinal paths of travel of the slides 15 and of the grinding wheels in conformity with the longitudinal direction of the tooth surfaces to be ground. This is clearly shown in Fig. 3, where the slides 15 are shown as adjusted so that the grinding wheels 5 and 6 will reciprocate along paths 41 and 42, respectively, which converge in a point .r and are inclined to one another at the same angle as the angle of convergence of the sides 37 and 38 of the teeth of the tapered gear G being ground.

' The rough-grinding operation is efiected by rotating the grinding wheels 5 and 6 on their axes and simultaneously reciprocating the wheels across the face of the gear G while producing a relative rolling motion between the wheels and gear to generate the tooth profiles. For bevel gears, therolling motion may be produced through the mechanism forming part of the machine of the Finsen et al application. When the sides of a tooth have been ground, the wheels are withdrawn from engagement with the gear and the gear is indexed asin the ordinary operation. The wheels are then moved into engagement with the next tooth of the gear and this is ground and the operation proceeds as before until all of the teeth have been rough-ground.

There may be more than one rough-grinding operation, but the wheels will simply be fed laterally between successive rough-grinding operations in order to remove more stock.

After the rough-grinding operation has been completed, the wheels are readjusted relative to the gear as shown in Figs. 2 and 4. The conical operating surfaces of the wheels are moved out of operative position and the plane sides 9 and 10 of the wheels are brought into operative position. This is done by spreading the wheels far enough apart so that their conical surfaces 7 and 8, respectively, no longer engage opposite sides 37 and 38 respectively, of a tooth 40 of the gear, but their plane sides 9 and 10, respectively, are brought into engagement with opposite sides 38 and 37, respectively, of alternate teeth 39 and 41, respectively, of the gear. The wheels are also readjusted relative to one another so that their axes are inclined to one another at the angle required to incline the plane sides 9 and 10 of the wheels to thepitch surface. of the gear to produce the required pressure angles'on the finished tooth surfaces. The arms '16 and 17 of the machine are also readjusted to change the angled convergence ofthe wheel paths as required by reason of the fact that the wheels are now to. grind opposite sides of alternate teeth of the gear. To obtain the first described angular adjustment in the Finsen machine, the wheel heads 14 may be mounted upon plates (not shown) that-are adjustable .angularly on the tool slides 15, as will be obvious to anyone skilled in the art.

For the finish-grinding, the wheels are rotated on their respective axes and simultaneously a relative rolling motion is produced between the wheels and gear to generate the tooth profiles. If the wheels are of sufiiciently large diameter, they do not have to be reciprocat'ed across the face of the gear, but will have their planes of action simply inclined to one another atthe angle corresponding to the angle between the sides 38 and 37.of alternate teeth of the gear and defined by the lines 45 and 46 in Fig. 4. If desired, however, the wheels may actually be reciprocated along the paths 45 and 46.

When the sides 37 and 38 respectively, of alternate teeth 39 and 41 have been ground, the wheels will be withdrawn from operating position and the gear indexed. The wheels will 7 then be moved back into engagement with the gear to grind other pairs of opposite side tooth surfaces of the gear and the alternate grinding and indexing will proceed until all of the teeth have been finish-ground.

Due to the fact that in the'finishing operation the wheels grind upon opposite sides of alternate teeth of the gear whereas in the roughing operation they grind upon opposite sides of the same tooth, any errors in spacing of the teeth which may occur by reason of wear of the wheels in the rough-grinding operation will be compensated for and eliminated in the finish-grinding operation. I This results from thefact that the teeth which are, respectively, the first and last to be ground in the rough-grinding operation are not the same teeth which are ground first and last, respectively, in the finish grinding operation.

Forthe purposes of clearness in disclosure, the invention has been described in connection with the grinding of straight bevel gears on aparticular type of straight bevel gear grinder. It will be obvious, however, that the invention is not limited to practice with this machine. The invention may be applied equally to thegrinding of spur gears as well as to the grinding of tapered gears and any suitable type of machine may be employed for either purpose with any suitable type of generating mechanism.

It is to be noted that in the'grmding of spur gears, it is not necessary, of course, to change the directions of the paths of reciprocation of the grinding wheels between the rough and finish grinding, for whether straight .or helical spur gears are being ground the wheels reciprocate in parallel paths both in the roughing and in the finish-grinding operations. The wheels are simply spaced further apart in the finish-grinding in order to grind opposite sides of spaced (alternate) teeth of the gear.

ciprocating the In general, it may be said that the invention is capable of various modifications and uses, and this application is intended to cover any variations, uses, or adaptations of the invention following, in'general, 'the principles of the invention and including such departures from the present disclosure as come within known or customary practice in the gear art and as may be ap-' what I between the wheel and the gear, and then finishgrinding the same tooth surfaces with a grinding wheel having a plane operating surface by rotating the wheel on its axis while simultaneously producing a relative rolling generating movement between the wheel and the gear.

2. The method of grinding the tooth surfaces of a gear which comprises, first, rough-grinding the tooth surfaces witha grinding'wheel having a conical operating surface by reciprocating the wheel across the face of the gear while rotating the wheel on its axis and simultaneously producmg. tween the wheel and. the gear, and then finish grinding the same tooth surfaces with a grinding wheel having a plane operating surface by rewheel across the face of the gear while rotating the'wheel on its axis and simultaneously producing a relative rolling generating -movement between the wheel and gear.

having a conical surface on one side and aplane surface on the other, rough-grinding the tooth surfaces with the conical side o the wheel by reciprocating the wheel across the face of the gear while rotating the wheel on its axis and producing a relative rolling generating movement between the wheel and gear, repositioning the wheel relative tothe gear, and then finish-grinding the tooth surfaces with the plane side of the wheel in a rolling generating operation.

4. The method of grinding the tooth surfaces of a gearwhich comprises'employing 'a' grinding wheel having a conical surface on one side and a plane surface on the other, first rough-grinding the tooth surfaces by positioning the conical side of the wheel in operative relation with the tooth surfaces and reciprocating the wheelacross the face of the gear while producing a relative rolling movement between the wheel and the gear, then finish-grinding the same tooth surfaces by positioning the plane side of the wheel in operative relation with the tooth surfaces and reciprocating the wheel across the face of the gear while rotating the wheel on its axis and producing a relative rolling movement between the wheel and the gear.

5. The method of grinding a gear which comprises employing a pair of grinding wheels. each of which has a conical grinding surface on one side and a plane grinding surface on the other side, first positioning said wheels so that the conical sides thereof are in operative engagement, respectively, with opposite sides of the same tooth a relative rolling generating movement beof the gear, and rough-grinding the tooth surfaces by reciprocating the wheels across the face of the gear while rotating the wheelsontheir axes and producing a relative rolling generating movement between the wheels and the gear, then repositioning the wheels so that their plane grinding surfaces are in operative engagement, respectively, with opposite sides of spaced teeth of the gear and rotating the wheels on their axes while producing a relative rolling generating movement between the wheels and gear.

6. The method of grinding a gear which comprises employing a pair of grinding wheels, each of which has a conical grinding surface on one side and a plane grinding surface on the other, first positioning said wheels so that the conical sides thereof are in operative engagement, respectively, with the sides of the same tooth of the gear, and rough-grinding the tooth surfaces by reciprocating the wheels across the face of the gear while rotating the wheels on their axes and producing a relative rolling generating movement between the wheels and the gear, then repositioning the wheels so that their plane grinding surfaces are in operative engagement, respectively, with opposite sides of spaced teeth of the gear and reciprocating the wheels across the face of the gear while rotating them on their axes and producing a relative rolling generating movement between the wheels and gear.

7. The method of grinding a gear which comprises employing a pair of grinding wheels, each of which hasa conical grinding surface on one side and a plane grinding surface on the other, first positioning said wheel so that the conical sides thereof are in operative engagement, respectively, with opposite sides of the same tooth of the gear, and rough-grinding the tooth surfaces by reciprocating the wheels across the face of the gear by rotating the wheels on their axes and producing a relative rolling generating movement between the wheels and gear, then repositioning the wheels so that their plane grinding surfaces are in operative engagement, respectively, with opposite sides of alternate teeth of the gear and rotating the wheels on their axes while producing a relatively rolling generating movement between the wheels and the gear, then repositioning the wheels so that their plane grinding surfaces are in operative engagement, respectively, with opposite sides of alternate teeth of the gear, and reciprocating the wheels across the face of the gear while rotating them on their axes and producing ,-a relative rolling generating movement between the wheels and the gear.

9; The method of grinding a straight tooth tapered gear which comprises rough grinding the tooth surfaces of the gearwith a grinding wheel having a conical grinding surface by positioning said wheel so at its conical surface is inclined to the pitch ace of the gear at an angle determined by the pressure angle of the tooth surfaces to be, ground and reciprocating the wheel in a longitudinal path determined by the lengthwise direction of the gear .teeth while rotating the wheel on its axis and producing a relative rolling motion between the wheels and gear, and then finish grinding the same tooth surfaces with a grinding wheel having a plane grinding surface by positioning said wheel so that itsplane surface is inclined to the pitch surface of the gear at an angle determined by the pressure angle of the tooth surfaces to be ground and so that said plane surface is inclined to the axis of the gear in correspondence with the longitudinal direction of the tooth surfaces, and rotating the wheel in engagement with the gear while producing a relative rolling movement between the wheel and gear. 1

10. The method of grinding a straight tooth tapered gear which comprises rough grinding the tooth surfaces of the gear with a grinding wheel having a conical grinding surface by positioning said wheel so that its conical surface is inclined to the pitch surface of the ,gear at an angle determined by the pressure angle of the tooth surfaces to be ground and reciprocating the Wheel in a longitudinal path determined by the lengthwise direction of the tooth surfaces while rotating the wheel on its axis and producing a relative rolling motion between the wheel and gear, and then finish grinding the same tooth surfaces with a grinding wheel having a plane grinding surface by positioning said wheel so that its plane surface is inclined to the pitch surface of the gear at an angle determined by the pressure angle of the tooth surfaces to be ground, and reciprocating said wheel across the face of the gear in a longitudinal path determined by the lengthwise direction of the tooth surfaces while rotating the wheel on its axis and producing a relative rolling motion between the wheel and gear.

a 11. The method of grinding a straight tooth tapered gear which comprises employing a pair of grinding wheels each of which has a conical grinding surface on one side and a plane grinding surface on the other, rough grinding the tooth surfaces of the gear by positioning the conical sides of the wheels in operative engagement with opposite sides of the same tooth of the gear with their conical surfaces inclined to the pitch surface of the gear in accordance with the pressure angle of the tooth surfaces to be ground, and reciprocating the wheels across the face of said gear in longitudinal paths converging in accordance with the-angle of convergence between opposite sides of a tooth of a gear-while rotating the wheels on their axes and simultaneously producing a relative rolling motion between the wheels and gear, andthen finish grinding the tooth surfaces of the gear byrepositioning the grinding wheels so that their plane sides are in engagement, respectively, with opposite tooth sides of alternate teeth of the gear with the plane sides of the wheels inclined to the pitch surface of the gear in accordance with the pressure angles of the tooth surfaces to be ground with the planes of said wheel-surfaces inclined to one another in accordance with the angle of convergence of the tooth sides being ground and rotating the wheels on their axes while producing a relative generating rolling movement between the wheels and gear. v

12. The method of grinding a straight tooth tapered gear which comprises employing a pair of grinding wheels each of which has a conical grinding surface on one side and a plane grinding surface on the other, rough grinding the tooth surfaces of the gear by positioning the conical sides of the wheels in operative engagement with opposite sides of the same tooth of the gear with the conical sides of the wheels inclined to the pitch surface of the gear in accordance with the pressure angles .of the tooth surfaces to be ground, and reciprocating the wheels across the face of the gear in longitudinal paths converging in accordance with the angle of convergencebetween opposite sides of the teeth of the gear while simultaneously producing a relative rolling motion between the wheels and the gear, and then finish-grinding the tooth surfaces of the gear by repositioning the grinding wheels so that their plane sides are in engagement, respectively, with opposite tooth sides of alternate teeth of the gear with the plane sides of the wheel inclined to the pitch surface of the gear in accordance with the pressure angles of the tooth surfaces to be ground and with the planes of said surfaces inclined to one another in accordance with the angle of convergence of the tooth sides being ground, and reciprocating the wheels across the face of the gear in paths converging correspondingly while rotating the wheels on their axes and simultaneously producing a relative rolling motion between the wheels and gear.

ARTHUR L. STEWART.- 

